In addition to the problems mentions by yongjik, even with the current system, very little software is even aware that the same codepoint should be rendered differently in different languages (返す needs to be rendered differently in every CJK locale) which often results in websites and programs using Chinese fonts for Japanese text (even if you've configured your language as Japanese). Having stroke breakdowns would not make this situation better because there are multiple ways to render the same stroke description and there aren't really systematic rules for how to correctly represent the Japanese (or Taiwanese or Korean) version of a character -- it's generally for historical reasons. If you were to try to actually represent the characters faithfully (in an attempt to avoid making every country unhappy with the way you've butchered their language), many characters would become unusable for text searching because the same "character" (from the perspective of a CJK native) would have a completely different representation in a way that a computer could not be able to identify as being the same (even a character as simple as 言う would have this issue).
I dread to think what an enormous mess would result if every character was represented as a build-it-yourself instruction manual rather than allowing font authors to correctly represent the characters. This is also ignoring that (depending on the font style), the apparent strokes for a character can change between fonts in the same language (this is because the computer font stroke style and the written font stroke style can be different) -- by putting stroke decisions in the encoding you're introducing a layering violation since fonts should be deciding how characters are styled, not encoding format committees.
Also nobody in China, Japan, nor Korea would switch to an encoding system so incredibly inefficient that more strokes results in more bytes being necessary to store the character (they already compromised with having 3-byte UTF-8 characters when JIS, GB, and Big5 all only required 2 -- and Japan was basically forced to compromise on Han Unification). This would've resulted in the failure of Unicode's mission to be the One True Encoding Format.